1. Field of the Invention
The present invention relates to a quantum cascade laser.
2. Description of the Related Art
Jpn. J. Appl. Phys., vol. 39, pp. L1297-1299, 2000 (Non-Patent Document 1), Journal of Modern Optics, vol. 52, No. 16, pp. 2303-2308, 2005 (Non-Patent Document 2), and Jpn. J. Appl. Phys., vol. 39, pp. 3406-3409, 2000 (Non-Patent Document 3) disclose quantum cascade lasers. In particular, Non-Patent Document 2 discloses a quantum cascade laser (QCL) including a mesa waveguide and a distributed Bragg reflector constituted by semiconductor/air. The distributed Bragg reflector reflects light emitted from the mesa waveguide.